1. Field of the Invention
The present invention relates generally to boilers or heaters for heating water, and more particularly to a transfer arm for transferring a fuel-air mixture from a blower to a burner inlet of the water heater.
2. Description of the Prior Art
One prior art water heater system which has been marketed by Lochinvar Corporation, the assignee of the present invention, is that sold as its KNIGHT™ heating boiler models KBN399 and KBN500. The KNIGHT™ heating boiler is a high efficiency condensing boiler. It utilizes a heat exchanger design marketed by the Giannoni Company of France, and constructed generally in accordance with the teachings of U.S. Pat. No. 7,267,083 to LeMer et al., the details of which are incorporated herein by reference.
The Lochinvar KNIGHT™ heating boiler has a horizontally oriented cylindrical combustion chamber defined within a primary heat exchanger. The primary heat exchanger is located in parallel above a secondary horizontally oriented heat exchanger. An elongated burner tube extends axially into the combustion chamber. A variable speed pre-mix blower is located above the combustion chamber for providing a fuel-air mixture to the burner at variable flow rates. A fuel-air transfer arm connects a blower outlet to an inlet of the burner. This prior art fuel-air transfer arm is shown in FIGS. 11-15, and is designated by the numeral 100. The fuel-air transfer arm 100 takes the fuel-air mixture supplied from the blower, turns it through a first sharp 90° turn 102, ducts it to a position adjacent the burner inlet, and turns the fuel-air mixture through a second sharp 90° turn 104 to direct it to the burner inlet.
The design of the KNIGHT™ boiler described above has been successfully utilized for boilers up to 500,000 BTU/hr output. We have discovered that when the general design of the KNIGHT™ boiler is scaled up to provide boiler outputs in excess of about 500,000 BTU/hr, problems are encountered in the flow of the fuel-air mixture to the burner, and the present invention is directed to the solution of those problems.